Ticket #3081: genericrelation_delete.patch

query.py

@@ -909 +909 @@
     return joins, where, params
 
 def delete_objects(seen_objs):
+    from django.contrib.contenttypes.models import ContentType
+    from django.db.models.fields.generic import GenericRelation
+
     "Iterate through a list of seen classes, and remove any instances that are referred to"
     qn = backend.quote_name
     ordered_classes = seen_objs.keys()
@@ -917 +920 @@
     cursor = connection.cursor()
 
     for cls in ordered_classes:
+        cls_content_type_params = []
+
         seen_objs[cls] = seen_objs[cls].items()
         seen_objs[cls].sort()
 
@@ -925 +930 @@
             dispatcher.send(signal=signals.pre_delete, sender=cls, instance=instance)
 
         pk_list = [pk for pk,instance in seen_objs[cls]]
-        for related in cls._meta.get_all_related_many_to_many_objects():
+        # Filter out GenericRelation related objects because there is no m2m table 
+        # for generic relation and there is no need to delete records from it.
+        # This also fixes issue in #2749 with deletion of both records from cls's table.
+        for related in (obj for obj in cls._meta.get_all_related_many_to_many_objects() 
+                            if not isinstance(obj.field, GenericRelation)):
             for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
                 cursor.execute("DELETE FROM %s WHERE %s IN (%s)" % \
                     (qn(related.field.m2m_db_table()),
@@ -933 +942 @@
                         ','.join(['%s' for pk in pk_list[offset:offset+GET_ITERATOR_CHUNK_SIZE]])),
                     pk_list[offset:offset+GET_ITERATOR_CHUNK_SIZE])
         for f in cls._meta.many_to_many:
+            query_add = ""
+
+            if isinstance(f, GenericRelation):
+                cls_content_type_params = cls_content_type_params or [ContentType.objects.get_for_model(cls).id]
+                query_add = " AND %s=%%s" % f.rel.to._meta.get_field(f.content_type_field_name).column
+
             for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
-                cursor.execute("DELETE FROM %s WHERE %s IN (%s)" % \
-                    (qn(f.m2m_db_table()), qn(f.m2m_column_name()),
-                    ','.join(['%s' for pk in pk_list[offset:offset+GET_ITERATOR_CHUNK_SIZE]])),
-                    pk_list[offset:offset+GET_ITERATOR_CHUNK_SIZE])
+                query = "DELETE FROM %s WHERE %s IN (%s)" % \
+                            (qn(f.m2m_db_table()), qn(f.m2m_column_name()),
+                            ','.join(['%s' for pk in pk_list[offset:offset+GET_ITERATOR_CHUNK_SIZE]]))
+                params = pk_list[offset:offset+GET_ITERATOR_CHUNK_SIZE]
+                cursor.execute(query + query_add, params + cls_content_type_params)
         for field in cls._meta.fields:
             if field.rel and field.null and field.rel.to in seen_objs:
                 for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):